Chlamydia trachomatis is the leading cause worldwide of preventable infectious blindness (trachoma) and sexually transmitted disease, including nongonoccocal, urethritis and pelvic inflammatory disease (PID). The PID is the leading cause of female infertility in this country. Recent research also indicates that Chlamydia infection may be responsible for some joint disorders and coronary heart disease. The chlamydial exoglycolipid antigen (GLXA) is expressed at all differentiation stages of the organism and is secreted from infected cells. Serum samples from patients infected with C trachomatic, C. pneumoniae and C pssittaci react with GLXAdemonstrating that it is a genus-specific, immunogenic antigen. This antigen is completely different from lipopolysaccharide (LPS). The major objective of this project is to determine the biochemical nature/structure of this GLXA antigen. The glycolipid GLXA will be analyzed by chemical and enzymatic digestion, in combination with Dionex-HPLC, Glyko-FACE, GC/M[S, M[ALDI-TOF MS and NMR.